I have had Brenda Hoddinott's Fine Art site listed for years (she used
to be a Getty list member). This Drawing Lessons site is fairly new. I
registered to try it out. All of the lessons I checked are free. You
can subscribe to get an ad free version.

Brenda helped a former student of mine who was going into forensic art.

I added links on the Art Education links page and on Art Teacher's Web Pages.

Poke around on this site and see if it will motivate your students.
Lots of step by step lessons to see.